Fig. 2. Expression of Odd1 in the mouse embryo. LacZ staining of mouse embryos heterozygous for the ß-galactosidase gene inserted into the Odd1 locus. At E9.5, Odd1 is expressed in the intermediate and part of the lateral plate mesoderm (A). In a section through the mesonephros (B), lacZ staining is present in the coelomic lining and mesenchyme, but is absent from the nephric duct and largely absent from the mesonephric tubules. (C) Schematic of events in metanephros formation: (left) invasion of the ureteric bud (white) into the metanephric mesenchyme (blue); (center) initial branching of the ureteric bud; (right), continued branching of the ureteric bud and formation of epithelial vesicles (yellow). See text for details. (D) At E10.5, Odd1 is expressed in the metanephric mesenchyme but not in the ureteric bud. (E,F) At E11.5, Odd1 is expressed in the undifferentiated condensed mesenchyme of the metanephros and at lower levels in mesenchyme surrounding the ureteric stalk, but not in ureteric bud derivatives. Odd1 is also expressed in mesenchyme adjacent to the ventral aorta (arrow in E). At E13.5 (G-I), Odd1 continues to be expressed in the condensed mesenchyme, but not in pretubular aggregates (H, arrow) or comma-shaped bodies (I, arrow). The lacZ staining in the ureter epithelium in G is non-specific. a, aorta; cm, condensed mesenchyme; d, nephric duct; du, ureter epithelium; m, mesonephric mesenchyme; mm, metanephric mesenchyme; s, ureteric stalk; t, mesonephric tubules; u, ureteric bud.